The invention relates to an independent rear suspension for a motor vehicle.
The prior art teaches that certain benefits are achieved through use of so-called xe2x80x9cindependentxe2x80x9d vehicle suspensions, in which the position of a given wheel relative to a vehicle""s chassis remains generally unaffected by the relative movement of another wheel on the vehicle. Generally, such independent suspensions employ xe2x80x9ccorner modulesxe2x80x9d that include a knuckle that is coupled by lateral and trailing links or xe2x80x9ccontrol armsxe2x80x9d to each of several attachment points defined on the chassis. Typically, a bushing or ball joint is utilized at the respective ends of each control arm to thereby pivotally couple the control arm to both the knuckle and the chassis. A coil spring and damper are typically disposed above the knuckle, between the knuckle and the chassis, to complete the corner module. The control arms together define the range of relative movement through which the knuckle and, hence, the associated wheelend assembly can travel as the knuckle is displaced vertically toward the chassis, including relative changes in longitudinal wheel location, wheel camber, and wheel toe-in, while the coil spring and damper cooperate to define certain parameters of such movement.
In certain vehicle designs that provide limited space above the wheelend assembly within which to locate the coil spring, the prior art has sought to utilize cantilevered leaf springs in place of the coil spring. Such cantilevered leaf springs generally extend from a location on the vehicle chassis either forward of, or transverse relative to, the nominal wheel location, and may even perform a dual function by replacing one of the corner module""s control arms, thereby advantageously reducing the associated parts count of the corner module.
Thus, for example, in U.S. Pat. No. 4,143,888, a leaf spring is nonrotatably coupled at either end to the chassis and the knuckle, respectively, to thereby provide a particularly compact structure in which the leaf spring acts as a trailing arm to constrain longitudinal movement of the wheelend assembly. However, the rigid attachment of the leaf spring to the vehicle frame, as taught in the ""888 patent, concentrates all reacting loads on the single chassis attachment point, thereby generating a large stress on the chassis. Further, because the rigid attachment of the spring to the frame provides no lateral, longitudinal, or torsional compliance, the leaf spring tends to constrain knuckle movement that might otherwise be achieved with the defined control arm configuration and, specifically, limit the range of available wheel camber and toe-in change achieved by such designs.
Accordingly, what is needed is an independent rear suspension for a motor vehicle featuring a reduced assembly height but providing a desired range of travel-induced changes in wheel camber and toe-in.
In accordance with the invention, an independent rear suspension for a motor vehicle chassis includes a pair of rear corner modules, each of which is adapted to be attached to a respective set of attachment points defined on the vehicle chassis. Under the invention, each rear corner module includes an elongated leaf spring having a forward end, a rearward end, and an intermediate portion between the forward and rearward ends. The forward end of the leaf spring is adapted to be rotatably coupled to the first forward attachment point, as by passing a pin through an eye integrally formed in the forward end of the leaf spring.
In accordance with an aspect of the invention, each rear corner module further includes one or, more preferably, two lateral links, each link having a respective first end that is adapted to be rotatably coupled to a respective transverse attachment point on the vehicle chassis. Each rear corner module also includes a knuckle adapted to rotatably support a wheelend assembly, with the knuckle being nonrotatably coupled to the rearward end of the leaf spring and rotatably coupled to the second ends of each of the module""s respective lateral links.
In accordance with another aspect of the invention, each rear corner module further includes a shackle coupled to the intermediate portion of the leaf spring and adapted to be pivotally mounted on the chassis at a second forward attachment point. The shackle maintains the intermediate portion of the leaf spring above the second forward attachment point, and at a predetermined distance from the second forward attachment point. The shackle provides a predetermined nonzero range of relative longitudinal, transverse, and torsional movement of the intermediate portion of the leaf spring relative to the second forward attachment point in response to a vertical displacement of the knuckle relative to the chassis. In this manner, the shackle provides lateral, longitudinal, and torsional (twisting) compliance for the intermediate portion of the leaf spring, relative to the vehicle chassis, that, in turn, creates a desired camber-change and wheel toe-in effect providing improved driving stability.
In accordance with yet another feature of the invention, in a preferred embodiment, the shackle consists of an eye that encompasses the intermediate portion of the leaf spring, and a tension member such as a bolt whose respective ends are pivotally attached to the shackle""s eye and the second forward attachment point on the chassis, as by passing the bolt through a slightly enlarged bore defined in each of eye and the attachment point. In this manner, the invention advantageously provides the resulting couple between the intermediate portion of the spring and the chassis with five degrees of freedom while otherwise restricting vertical movement of the intermediate portion of the spring by maintaining a predetermined distance between the intermediate portion of the spring and the second forward attachment point.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.